Van Aswegen, G.; De Vos, Valerius; Schoeman, J.H.; Van Noorden, Susan; Kotze, Sanet H.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1996)
Van Aswegen, G.; Schoeman, J.H.; De Vos, Valerius; Van Noorden, Susan(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1994)